Give calves their fill during winter’s chill

Keeping water lines thawed and moving snow aren’t the only extra tasks that Old Man Winter creates on the dairy. Carefully managing calf nutrition is another demand that requires attention during the frigid winter months.

“Newborn calves start out life with very minimal energy reserves,” says Mike Van Amburgh, associate professor of animal science at Cornell University. “Because calves have a higher surface-area-to- bodyweight ratio than older animals, they become cold-stressed at fairly moderate temperatures.”

He explains that at temperatures below the “thermoneutral zone,” calves start to expend their internal energy reserves simply to maintain their core body temperature of 102 degrees F. The result: energy resources are diverted from growth and immune function, meaning calves will not gain weight, and are more susceptible to diseases like pneumonia and scours.

Van Amburgh says the thermoneutral zone for Holstein calves three weeks of age is 68 degrees F to 82 degrees F, but at temperatures below 60 degrees F, calves have to increase energy expenditure to maintain body temperature. For calves from 22 days of age to weaning, it is approximately 42 degrees F, depending on insulation and rumen function. “When an 88-pound newborn calf has to start mobilizing its own fat stores to stay warm, it has less than one day’s worth of energy ‘in the bank,’” he notes.

Colder weather demands higher nutrition

To help calves survive and thrive in cold weather, diet is the first line of defense. Because young calves three weeks and under have little to no rumen function yet, nearly all of the required extra energy must come from a liquid feed source.

Whether milk replacer or pasteurized waste milk is the primary liquid feed source, calves will use more energy when temperatures drop. Van Amburgh says a traditional milk-replacer program of feeding 20 percent protein, 20 percent fat milk replacer at a rate of 1 pound of dry powder per day (2 quarts of milk replacer fed twice a day at standard dilution rates) will result in strictly maintenance for the calf, with no remaining energy for weight gain at temperatures below the thermoneutral zone.

Pasteurized whole milk fed at the same volume will provide 11 percent to 18 percent more energy due to its higher protein and fat content. However, consistency of nutrient levels in whole milk can vary considerably day-to-day, which requires careful monitoring of this feed source. Increasing nutrient levels in whole-milk feeding programs to accommodate for colder temperatures also may require supplementation with milk replacer, depending on the volume of waste milk available on the dairy.

Higher-protein milk-replacer rations fed at more appropriate rates provide considerably higher energy levels and allow calves to withstand colder temperatureswhile still gaining weight. Table 1 shows a comparison of a 20:20 milk replacer feeding program and a feeding program utilizing more of a 28 percent protein, 20 percent fat milk replacer. At 32 degrees F ambient temperature, calves on the 28:20 program still would be expected to gain 1.41 pounds per day, with no adjustments to the feeding program.

Van Amburgh advises working with a nutritionist to select and properly adjust liquid feed rations to accommodate for cold temperatures, noting that a 100-pound calf may require more than double the amount of 20:20 milk replacer powder per day to achieve one pound of gain per day at an ambient temperature of 5 degrees F.

“Feeding a fat supplement in cold weather is another common suggestion,” notes Van Amburgh. “Most of those products are 7 percent protein and 60 percent fat. Supplementing a standard, pound-per-day, 20:20 milk replacer ration with 0.25 pounds per day of a 7:60 fat source at 32 degrees F will increase the energy allowable to gain by just 0.22 pounds per day, which is just slightly above maintenance. Thus, feeding more of an appropriately balanced diet to meet the requirement for both energy and protein for allowable gain would be a more effective approach to compensate for cold stress.”

Provide housing that is draft-free with good air quality, and keep calves dry at all times.

Use deep straw bedding to give calves a place to “nest” and thus conserve body heat. Manyproducers also successfully use calf jackets to also help conserve body heat.

Feed liquids as close to the calf’s internal body temperature as possible. Most milk-replacermanufacturers suggest feeding at 100 degrees F to 105 degrees F. Supplying liquid feed orwater at much cooler temperatures requires the calf to expend energy to warm the liquid to itsinternal body temperature after consumption, and can increase bloat problems.

Offer a high-quality (20 percent protein or higher), free-choice starter grain to encourage rumen development and provide supplemental energy. The protein level of the starter should becommensurate with that of the liquid feeding program.

Provide warm, free-choice water to promote dry feed intake and improve digestion, weight gainand overall health of calves. While this can be challenging in the winter, offer water for 20 to30 minutes immediately post-feeding. Calves are still up and active at this time, which will helpto encourage intake within a timeframe that is manageable for then disposing of unconsumedwater before it freezes.

“Caring for calves in the winter provides its own set of challenges, to be sure,” says Van Amburgh. “But well nourished, properly housed calves can grow well and remain exceptionally healthy, even in the most extreme conditions, and we now know this is early growth has long-term benefits when they reach lactation.”

Table 1. Effect of cold stress on predicted calf growth using the 2001 Dairy NRC calf model (National Research Council, 2001). A 100-pound calf was used as the model animal